Design of state-variable SC filters by means of polynomial transformation

A simple polynomial transformation is presented which permits efficient computation of SC state-variable coefficients directly from
Z
-domain specifications. The algorithm relies merely upon synthetic division. The technique is applied to synthesize a fourth-order elliptic filter using only forward difference integrators (FDI), or, alternatively, only backward difference integrators (BDI). A specific state-variable topology, the so-called observer canonical form, was chosen; the technique, however, is more generally applicable. The use of a single SC integrator topology permits a significant reduction in the number of switches. Experimental results are presented which demonstrate the practical utility of the method.